Stuart posted about the quickly vanishing Amazon deal on the DS300 ToughSystem large box a few days ago. Another reader beat me to it in the comments, but it appears at least some Home Depots have these same boxes on sale for $39.
If you look on the Home Depot website, these boxes are listed for $59. So it’s an in-store thing.
YMMV, I can’t guarantee that every local HD has this deal, but we’ve verified 2 different stores in two different areas.